The present invention relates to a device for the uniform dosing of amounts of faeces onto reagent papers.
The recognition of component materials in faeces, especially of blood, has recently achieved increasing importance, for example in the case of control investigations. For this purpose, test papers containing guaiac resin as an indicator have proved to be particularly useful.
For the detection of blood in faeces, the latter are applied to a reagent paper and, after drying, development is carried out with an alcoholic solution of hydrogen peroxide. The reagent papers are either supplied in the form of rolls or are struck into pieces of cardboard provided with an opening for the introduction of the faeces.
In practice, it has been found that, even in the case of a precise description of the manner in which the faeces are to be dosed, even well trained operators have great difficulty in applying standardized amounts of faeces to the test paper in order to achieve reproducible results.
Investigations have now shown that the sensitivity of the test papers depends decisively upon the amount of faeces applied, which is not surprising since the exactitude of an analytical method depends, in the first place, upon the dosing of the sample.
In the case of commercially available diagnostic agents for determining the component materials of body fluids, a uniform sample dosing does not give rise to any difficulties. As is well known, it is ensured by the take up of fluid by the test area.
In the case of faeces, however, because of the viscosity thereof, which is higher than that of body fluids, the amount of sample must be applied by the user directly to the reagent paper. Therefore, a continuously uniform dosing is not ensured. It would be obvious to cover test papers for the detection of component materials of faeces with a device which is to be filled with faeces. This device must be constructed in such a manner that, in the course of filling, the user is more or less obliged to apply a standardized amount of faeces. For example, this may be a template provided with a circular opening which thus has a cylindrical shape. Models have been devloped but, in practice, it has been found that such models are not suitable, for example, for the conventional testing of faeces.
As is also known, in the case of methods for the detection of blood in faeces with the help of reagent papers, the sample must be developed with an alcoholic solution of hydrogen peroxide which is applied dropwise to the rear side of the coated paper. In the course of the development process, the chromogen present in the reagent paper is oxidized by the catalytic action of the hemoglobin in the blood to give a blue-colored material. The colored material chromatographs out from the faecal sample, depending upon the shape of the faecal sample, are more or less irregular and appear to the observer as one or more blue zones. If, over the test paper, there is applied a second and somewhat thicker layer of paper, for example cardboard, in which is stamped a circular opening, then a cylinder is provided which is filled with the faeces to be investigated. In this way, while the user always applies a uniform amount of the faeces to be investigated, it has been found that the color development, in comparison with a detection test in which the same amount of the same faeces is employed but without the cylinder, is considerably inhibited and the reaction appears, therefore, to be insensitive.